#include <reg52.h>
#define uchar unsigned char
#define uint  unsigned int
sbit fmq=P3^6;

void delay500us()
{
	uchar j;
	for(j=0;j<57;j++){;}
}
void main()
{
	uint t;
	while(1)
	{
		fmq=0;
		delay500us();
		fmq=1;
		delay500us();
	}
}